Simple Mail Transfer Protocol (SMTP) Mailers (System Administration Guide: Resource Management and Network Services)

System Administration Guide: Resource Management and Network Services

SMTP is the standard mail protocol that is used on the Internet. This protocol defines these mailers.

smtp provides regular SMTP transfers to other servers.
esmtp provides extended SMTP transfers to other servers.
smtp8 provides SMTP transfers to other servers without converting 8–bit data to MIME.
dsmtp provides on-demand delivery by using the F=% mailer flag. Refer to Changes to the MAILER() Declaration and New Delivery Agent Flags in Chapter 27, What's New With Mail Services (Reference).